Busche, E. (Corresponding author)FZJ*

1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-3375

Abstract: The quantitative measurement of ion temperatures is of great relevance for the interpretation of experiments related to controlled fusion research. The diagnostics, which have been developed for this purpose, are often indirect and have to be checked for consistency. For spectrocopic diagnostics this concerns in particular the comparison between measurements on impurities with those on the Hydrogen isotopes. Charge exchange recombination spectroscopy (CXRS) is a diagnostic, which allows the determination of radial resolved ion temperatures. The analysis of the H- or D-spectra are problematic because of several effects. For this reason, normally spectra of light impurities are used for CXRS. In this report the charge exchange spectrum of Hand D is analysed and the results are compared to other independent measurements. The two effects, which are the most important for complicating the analysis, are the dependence of the effective emission coefficient on the collision energy and the halo effect. Both have been simulated numerically. In the case of the O"cx(Ered-dependence it is shown, that for the parameter range of TEXTOR the resulting spectrum can be approximated with a gaussian. For the calculation of ion temperatures and toroidal velocities correction values have been introduced with the species distribution of the neutral beam particles taken into account. A numerical transport model has been developed for the halo effect. With this the density and temperature distribution of the neutral H or D particles surrounding the neutral beam was calculated and the resulting spectra were simulated. The conclusionis that the halo has a large influenceon the locality of the measurement and contributes significantly to the measured photon flux, but that the influence on the measured temperature profile is larger than other typical experimental errors only at the plasma edge. Under different plasma conditions Da-spectra have been measured and analysed. A general trend is a central ion temperature, which lies above the electron temperature for neutral beam heated discharges. The shape of the radial profiles did not depart significantly from the Te-profiles. The impurity ion temperatures, which have been evaluated from CXRS spectra of CVI and Nex, were higher than the D temperatures in the case of higher temperatures and lower densities. For lower temperatures and higher densities, as eg in the case of radiative I-mode discharges, the temperatures agreed within the typical error bars

Keyword(s): plasma diagnostics ; spectroscopy ; Textor Tokamak

1. Plasmaphysik (IEF-4)